It is known to use a purge bubbler to determine the height of a liquid in a wetwell or the like. It is also known to determine the back pressure in a bubbler tube by using an apparatus with a flat plate manometer having vertically stacked level-sensing contacts which are reached by liquid mercury as it rises up the manometer. The rising mercury closes a circuit between a common contact and the various contacts along the vertical column, and the height of the liquid in the container is then determined on the basis of which contact is the highest contact closed by the mercury. U.S. Pat. No. 4,297,081, issued Oct. 27, 1981 to Irvin, is exemplary of this prior art approach.
Two other patents of interest in this area are the following:
U.S. Pat. No. 4,380,933, issued Apr. 26, 1983 to Irvin, PA0 U.S. Pat. No. 3,947,692, issued Mar. 30, 1976 to Payne.
The prior art developments are generally cumbersome methods of determining the height of a liquid in a container or wetwell. Accordingly, it is an object of one aspect of this invention to provide a simplified but reliable, self-contained apparatus which can be immersed in a liquid, and which is adapted to provide a reliable signal representing the height of the liquid in a wet well.